ci: harden R2 canary cleanup and coverage

[teamleaderleo]

Problem

The canary cleanup deleted its R2 artifact once. A transient remote-delete failure could leave the bucket non-empty, so bucket deletion failed and the per-run bucket remained allocated until its lifecycle rule expired. The canary job also had too little timeout margin, cleanup treated an absent secret as an error after partial deploys, and transport checks did not run on pushes that changed .github/workflows/ci.yml alone.

Change

• Retry the exact canary artifact deletion up to four times with short backoff before bucket cleanup.
• Treat only Cloudflare HTTP 404 responses as an idempotent absent-secret cleanup; preserve other failures.
• Increase the isolated canary job budget from 15 to 20 minutes.
• Include .github/workflows/ci.yml in the main push path filter.
• Add regression coverage for cleanup semantics, workflow coverage, timeout budget, and artifact-delete retries.

Validation

• python3 tests/test_ci_r2_canary.py (20 tests)
• git diff --check

[github-actions]

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[coderabbitai]

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📥 Commits

Reviewing files that changed from the base of the PR and between 3f542e8 and 9fd4f91.

📒 Files selected for processing (3)

• .github/workflows/ci-artifact-canary.yml
• scripts/ci/r2-canary-cloudflare.py
• tests/test_ci_r2_canary.py

✨ Finishing Touches 💡 1

🛠️ Fix failing CI checks 💡

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• Create a new PR

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[greptile-apps]

Confidence Score: 5/5

The PR appears safe to merge; the only remaining concern is a non-blocking gap in the exact artifact-key regression assertion.

Summary

This PR hardens the R2 canary cleanup path and expands its regression coverage.

• Retries remote artifact deletion four times with incremental backoff before bucket removal.
• Treats only Cloudflare 404 responses as successful idempotent secret cleanup.
• Increases the canary timeout and runs transport checks when the main CI workflow changes.
• Adds executable coverage for retry count, backoff, and terminal status.

Diagram

%%{init: {'theme': 'neutral'}}%%
flowchart TD
  A[Canary cleanup starts] --> B[Delete artifact]
  B -->|Success| C[Delete empty bucket]
  B -->|Failure and attempts remain| D[Back off]
  D --> B
  B -->|Fourth failure| E[Fail artifact cleanup]
  E --> C
  C --> F[Delete worker secrets]
  F -->|HTTP 404| G[Treat secret as already absent]
  F -->|Other error| H[Preserve cleanup failure]

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[teamleaderleo]

Resolved the conflicts in 9fd4f91. The branch carried obsolete upstream history; the merge preserves current main and the four-file canary change, rather than restoring unrelated old code. One trigger change was already on main, leaving three changed files. All 20 canary tests, both workflow lint checks, and independent review pass. GitHub confirms the updated head is mergeable. Hosted native failures still require separate validation; no R2 deployment or activation was performed.